Moon is 100 million years younger than previously thought - Science Recorder

The long-ago time when Earth had no Moon isn't as far away as most scientists think, according to a new study based on analyses of Moon rocks. Whereas science has historically pegged the Moon's formation as having occurred around 4.56 billion years ago, the new study suggests the Moon actually formed between 4.4 billion to 4.45 billion years ago.
The Royal Society in London hosted a debut presentation of the study results Monday in a forum titled "Origin of the Moon." According to the presenter, Richard Carlson of the Carnegie Institution for Science in Washington, D.C., tools for analyzing samples of the Moon extracted from the Apollo lunar missions of the 1970s have grown more sophisticated over the years.

The technology that Earth's moon researchers use is the same as it was in the 1970s—now, as then, the researchers use radioactive carbon dating. But the latest tests, according to Carlson, indicate that earlier ones may have overestimated the rocks' age.

This new date for the Moon's birth still places it as having occurred before the rise of life on Earth, which scientists estimate to have happened around four billion years ago—the oldest known fossils of microbes is about 3.5 billion years old. That is a good thing, because the Moon's birth would have been a calamitous event for any life that was present on Earth at that point in time. According to the prevailing theory among astronomers, the Moon formed from a Mars-sized planet crashing into Earth and causing millions of tons of Earth's crust to fly out into space.

Some of that loose matter coalesced and formed the Moon. Computer simulations of this planetary collision indicate that the Moon ended up being 80% debris from Earth and 20% debris from the planet that collided with Earth. And as further evidence for the Moon's younger age, Carlson notes, researchers on Earth have found geological signs of a major melting event on our planet that occurred around 4.45 billion years ago.

This indication of a younger age for the Moon raises new questions about the processes of Earth's early formation, and that of other planets in deep space that are likewise subject to massive collisions, Carlson added. For instance, if the collision was more recent, Earth might have been further along in its formation when the collision occurred.
If so, then scientists may wonder if the collision blew off this primordial atmosphere into space. The reverberations would matter for the formation of our atmosphere up to the present day.